1. Field of the Invention
The present invention relates to a turbine exhaust system for introducing, to a condenser, exhaust steam after having driven a turbine rotor, and a method for modifying the same.
2. Description of the Related Art
In a steam turbine plant having a condenser, steam (exhaust steam) after having conducted work inside a turbine is generally condensed by a condenser and circulated after having being subjected to a pressure recovery through an exhaust hood. The inner pressure of the condenser is principally defined by a temperature of seawater serving as cooling water and a flow rate thereof. Therefore, the larger the extent of pressure recovery in the exhaust hood, the lower is the back-pressure at a blade path exit plane. Correspondingly, work load on the turbine increases, and power generation obtained by driving the turbine increases. Hence, the pressure recovery performance of the exhaust hood has a large effect on turbine plant performance.
As an example of this type of exhaust hood, JP. A 52-93809 discloses an exhaust hood in which an exhaust hood outer casing is divided into an upper half casing and a lower half casing, with the neighborhood of the horizontal plane containing the central axis of the turbine rotor as a boundary, and in which a flow path, to the condenser, of exhaust steam discharged into the upper half casing and a flow path thereto of steam discharged into the lower half casing are separated from each other by a partition wall. According to this conventional art, by dividing the exhaust steam discharged into the upper half casing and that discharged into the lower half casing by the partition wall to divide a flow amount of exhaust steam into two, the flow proportion of exhaust steam flowing in the exhaust hood is properly adjusted, thereby promising to improve performance of the exhaust hood.